Cellulose acetate films (which may be referred to as “acetate film” or “cellulose acetate film”) are widely used as a film base for information storage due to their stability and long-term storage capacity (e.g., N. S. Allen et al, J. Photogr. Sci. 36, 194–198, 1988).
However, recently, there has been a problem in that, depending on the way the film is stored, the deterioration progresses more seriously than expected. As one of the reasons for this deterioration process, the presence of free (released) acids (especially acetic acid) resulting from decomposition of the film base has been mentioned. In particular, it was found that when these free acids exceeded a specific value (threshold value), the deterioration was accelerated rapidly. This phenomenon is referred to as “vinegar syndrome”, and is thought to be a kind of autocatalyzed hydrolysis reaction by acid.
Although methods have been proposed to solve this deterioration problem by washing the film with water or an alkaline solution and drying, or neutralizing with ammonia gas, deterioration was not sufficiently suppressed, and the qualities of the film were spoiled, which was problematic.